| 摘要 |
<p>PURPOSE:To obtain a single-chip microcomputer having an action mode which is opened to users by increasing the action mode to be set without increasing the number of terminals. CONSTITUTION:In case the output signal levels a2 and a3 of flip-flops 4 and 5 are initialized at low values after reset initialization, the value of a chip 3 is set at (000) or (100) after the reset initialization (a1, a2, a3) based on the input level of a control signal. Then a ROM extension mode can be defined with (a1, a2, a3)=(100) as long as a single-chip mode is defined with (a1, a2, a3)=(000). Then it is possible to obtain four types action modes (001), (101), (011) and (111) that are available with a manufacturer only when a flip-flop 5 is set at a high level (unopened) by a program and the output signal of a3 is set at a high level.</p> |
